This paper studies the influence of different cooling technologies on the power density of a traction machine for heavy-duty distribution transport. A prototype induction machine is built with a housing cooling jacket, potted end-windings, entire winding cooling, and shaft cooling. Electromagnetic finite element and thermal lumped-parameter models are parameterized and verified using test bench measurements. The influence of each thermal resistance along the heat paths is studied and discussed. The results are used for studying different cooling technologies. The results indicate an improvement of the continuous power density up to 108% using shaft cooling and up to 15.6% using entire winding cooling.